Currently, the number of satellites launched by human is about 6,000. Among them, about 3,500 satellites are normally operating. Low earth orbit satellites present at 1500 km or lower from the earth among the satellites having expired lifespans lower their altitudes to enter the atmosphere. Most of the small satellites among the low earth orbit satellites are combusted in the atmosphere and disappear.
However, in contrast to the low earth orbit satellite, when lifespan of geostationary orbit satellite positioned at about 35,786 km from the earth is expired, the geostationary orbit satellite moves up from its position by 300 km by using last of its residual fuel in order to prevent collision with a newly lunched satellite or other satellites. Accordingly, the geostationary orbit satellite whose lifespan is over cannot be positioned on the geostationary orbit any more. As described above, an orbit higher than the geostationary orbit by about 300 km is called a graveyard orbit, and is also called a supersynchronous orbit or a junk orbit.